Thermophysical characterization of paraffin-based PCMs for low temperature thermal energy storage applications for buildings

Abstract

Trustworthy information about the thermophysical properties of phase-change-materials (PCMs) is vital for designing low temperature thermal energy storage systems for buildings and for modelling their thermal behaviour. However, data provided by manufacturers are recurrently optimistic, insufficient and/or uncertain for developing reliable numerical approaches, which requires further investigation. This paper aims to assess the key thermophysical properties of ten paraffin-based PCMs: microencapsulated and bulk paraffins.The melting/solidification peak temperatures, the enthalpy of fusion/solidification and the specific heat capacity were measured by Modulated-Differential-Scanning-Calorimetry. The Transient-Plane-Source-method was used to estimate the variations of the thermal conductivity/diffusivity with temperature. The thermal stability was assessed by High-Resolution-Thermogravimetric-Analysis. The microstructures of the microencapsulated PCMs were examined via Scanning-Electron-Microscopy.It was concluded that some information provided in the datasheets is roughly corroborated by the experimental results. However, in some cases, it was too optimistic (particularly the enthalpy of fusion/solidification), incoherent (mainly the melting/solidification peak temperatures) or scarce (e.g., the values of the thermal conductivity and the specific heat of the solid/liquid phases). The major contribution of this work is a reliable dataset for upcoming numerical modelling, saving time and resources in future studies. The results can also be used as a reference for future inter-laboratorial comparison studies.